As integrated circuit devices have become more complex, their die sizes have increased even though transistor sizes have been decreasing. This is so because of the increased demand for performance, functionality and integration into today's integrated circuits. To accommodate the increased die sizes of integrated circuits, the actual sizes of wafers used in semiconductor manufacturing of integrated circuits has been increasing as well to manufacture a reasonable number of the large die sizes simultaneously. It is not uncommon to talk about integrated circuits being one inch by one inch and manufactured on a wafer having a diameter of twelve inches or more. While wafer sizes have increased, they have not kept up with the demand for die size increases of integrated circuits. As a result, the number of dies of an integrated circuit on one wafer (die per wafer) has been decreasing. Thus, the yield of each individual die of the integrated circuit across a wafer is important in order to lower costs and obtain higher profit margins. Yield is even more important when memory circuitry having memory cells is included. The memory cells tend to be more sensitive to certain types of defects in semiconductor manufacturing because of their dense transistor circuitry.
Memory integrated circuits, such as random access memory (RAM) integrated circuits and read only memory (ROM) integrated circuits, typically have a rated capacity such as thirty two megabytes or sixty-four megabytes. The entire rated capacity needs to be functional in order to sell the memory integrated circuit. Thus, manufacturers of memory integrated circuits usually provide redundant rows and/or redundant columns of memory cells to substitute in for a bad row or bad column of memory cells.
Bad rows or bad columns in a memory integrated circuit are typically discovered during wafer testing prior to packaging the memory integrated circuit. In this case, fuses or links in the memory integrated circuit can be cut by a laser to substitute in a redundant row or a redundant column of memory devices for a respective bad row or bad column.
Other types of integrated circuits which are not a memory integrated circuit may include some memory circuitry therein. Typically if any part of the memory circuitry therein was tested to be defective, the entire integrated circuit was marked as being defective and discarded.
Today some integrated circuits, including micro-processor integrated circuits, micro-computer integrated circuits, application specific integrated circuits, custom integrated circuits, digital signal processing integrated circuits, and application specific signal processing integrated circuits, commonly have large blocks of memory circuitry therein such as one to sixteen megabytes or more of memory. Because the memory circuitry has become much larger in these integrated circuits, it can cause a higher rate of failure.
Like reference numbers and designations in the drawings indicate like elements providing similar functionality.